Bushido, the samurai code of ethics, was formalized in writing in the sixteenth century and adhered to for some three hundred years. Bushido placed emphasis on certain chivalrous virtues such as loyalty, courage, and courtesy.
Japanese sword shapes and their history.
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Samurai sword types
Hamon (from Japanese, literally "blade pattern") is a visual effect created on the blade by the hardening process. The hamon is the outline of the hardened zone (yakiba) which contains the cutting edge (ha). Blades made in this manner are known as differentially hardened. This difference in hardeness results from clay being applied on the blade prior the cooling process (quenching).
Shark teeth katana
Jeffrey Mallari Samurai Warrior 2013 Arizona Renaissance Festival by gbrummett, via Flickr